US BB in Europe - safe to go given market conditions?

I currently work in a mid-tier European bank and recently got an offer at a US BB (think Citi / BAML) in London.

While the opportunity and offer itself are much better than what I currently have, I am always worried about job security given we are most likely at a market downturn (and from what I've heard, historically US banks are the first to downsize their European offices at a bear market).

For reference, I'd be joining as an Associate.

Any advice whether I should be worried or not?